Russian jets launched strikes in Syria for a second day on October 1, saying Islamic State (IS) militants had been targeted, but the areas hit appeared to be held by groups opposing the IS group and the Syrian government.

The continuing attacks have deepened U.S. and Western fears that Moscow’s actions in Syria are aimed at propping up the regime of Syrian President Bashar al-Assad, and could potentially target U.S.-backed rebels who have been fighting to oust Assad.

In Moscow, the Defense Ministry said Su-24Ms and Su-25s aircraft had hit more than 12 Islamic State positions since September 30.

It said overnight strikes targeted an ammunition depot near Idlib, a three-story IS command center near Hama, and a facility located in the north of Homs aimed at rigging cars with explosives for suicide attacks.

The airstrikes, along with weeks of military buildup around the Latakia airbase in western Syria, constitute Moscow's largest intervention outside the former Soviet Union since the 1980s war in Afghanistan.

The ministry also said the warplanes had strictly avoided bombing populated areas. But the British-based Syrian Observatory For Human Rights said strikes in the province of Hama hit locations controlled by the U.S.-backed rebel group Tajamu Alezzah. It said the group was also targeted on September 30.

Hassan Haj Ali, the commander of the rebel group Liwa Suqour al-Jabal, which received military training from the CIA, said one of its training camps located in Idlib Province was hit.

And in an interview on CNN, U.S. Senator John McCain, head of the Senate Armed Services Committee, said that Russia's initial strikes targeted recruits of the Free Syrian Army rebel group backed by the United States.​

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Idlib Province is controlled by an Islamist alliance known as the Army of Conquest, which includes Al-Qaeda's affiliate in Syria, the Al-Nusra Front, and the hard-line Islamist group Ahrar al-Sham, and several more moderate Islamist groups. All have fought against the Islamic State group.

The risk of an accidental clash between Russian forces and the U.S.-led coalition has risen sharply after Russia launched its first strikes on September 30.

U.S. and Russian defense officials held talks on October 1 aimed at avoiding conflicts in Syria, but one top general said the United States will not share sensitive intelligence with Russia.

"I have a low level of trust in the Russians," Lieutenant General Robert Otto, an Air Force deputy chief of staff for intelligence, said. "I would not envision a relationship where I would share some of my intelligence with them."

Otto added that the Russians have been dropping "dumb bombs," munitions that are not precision-guided and are more prone to go astray and kill innocent civilians.

Russian Foreign Minister Sergei Lavrov told reporters at the United Nations on October 1 that Moscow shared the same approach as the U.S.-led coalition.

“If it looks like a terrorist, if it acts like a terrorist, if it walks, fights like a terrorist, it’s a terrorist, right? I would recall that we always are saying that we are going to fight ISIL and other terrorist groups. This is the same position that the Americans are taking,” said Lavrov, using an alternative acronym for the Islamic State group. “We see eye-to-eye with the coalition on this position.”

"We have the same approach: It's ISIL, Nusra and other groups," he added.

Lavrov also criticized comments by the U.S. Defense Secretary Ash Carter, who a day earlier likened Russian actions in Syria to "pouring gasoline on the fire."

"We are aware of many points of tensions where fuel was added to the fire, and it was the Pentagon who added this fuel in the entire region," Lavrov said.

Speaking late on September 30, U.S. Secretary of State John Kerry also expressed concern that Russia was hitting positions held by moderate foes of Assad, whom Moscow has given military and diplomatic support throughout a more than four-year war that has killed some 250,000 people.

"It's one thing to be targeting ISIL, but the concern, obviously, is that this is not what was happening," Kerry said.

The United States and France are targeting IS positions with air strikes in both Syria and Iraq.

The Syrian National Coalition, which includes opposition groups supported by the West, said Russian warplanes hit towns, resulting in the deaths of at least 36 civilians, including five children.

"It was very obvious that the Russian intervention was to support the regime, to support more killings inside Syria, and will create a more chaotic atmosphere,” the coalition's head, Khaled Khoja, said.

In a live broadcast from the Kremlin on October 1, President Vladimir Putin denied those assertions, calling them an "information attack."

Speaking on French radio on October 1, Russia's ambassador to Paris, Aleksandr Orlov, described allegations that the target of the air strikes was not IS positions as part of a "war of disinformation."

And Lavrov said, "The rumors that the target of these air strikes was not IS positions are unfounded."

"Talk began that civilians were hurt by air strikes. We have no such data," he added. "We carefully make sure that these target strikes are precise."

Kremlin spokesman Dmitry Peskov said on October 1 that Russia was going after IS militants and other "well-known" groups, and that the targets were chosen "in coordination" with the Syrian Army.

The purpose of the air strikes is "to support for the [Syrian] armed forces, which is fighting ISIL and other terrorist and extremist organizations."

He said Russia was targeting only "terrorist and extremist groupings."

According to the Russian Defense Ministry, more than 50 Russian warplanes and helicopters are part of the group conducting air strikes in Syria. A battalion of naval infantry is also guarding an air base used by the Russian Air Force near the Syrian port city of Latakia.

Russian President Vladimir Putin said on September 30 that Russia would be "supporting the Syrian Army purely in its legitimate fight with terrorist groups."

The United States and its allies insist that the Syrian president should leave office, while the Kremlin says he should remain in power.

"To simply defend Assad and not to pursue a political transition is only going to fuel the opposition and therefore the extremism and the violence," U.S. Defense Secretary Ashton Carter told reporters on September 30.

Saudi Arabia, a leading foe of Assad, demanded that the Russian strikes stop "immediately."

The Saudi UN ambassador, Abdallah Al-Mouallimi, said on October 1 that the strikes led to "a number of innocent victims and that countries should not be fighting IS militants at the same time as they support the terrorism of the Syrian regime."

Meanwhile, Iran's Foreign Ministry said Tehran "considers military action by Russia against armed terrorist groups to be a step toward fighting terrorism and toward resolving the current crisis" in Syria.

The RIA-Novosti news agency quoted the Russian Foreign Ministry as saying that Moscow would consider any request from Iraq to conduct air strikes against IS militants on Iraqi soil, but Lavrov said Moscow had not received any request.

"We are not planning to expand our air strikes into Iraq. No one has invited us or requested us about it," Lavrov said.